Dihedral angle fluctuations

The delocalization of the HOMO and LUMO arises from pseudo-ir orbital interactions between adjacent 3px and 3py atomic orbitals of Si atoms, respectively. Since the 3p orbital is on the Si-Si-Si plane, the degree of the interaction depends on the dihedral angle between adjacent Si-Si-Si planes. Fluctuation of the dihedral angles along the polymer skeleton then causes the so-called Anderson localization of the HOMO and LUMO [41]. 

Recently, the effects of static and dynamic structural fluctuations on the electron hole mobility in DNA were studied using a time-dependent self-consistent field method [33]. The motion of holes was coupled to fluctuations of two step parameters of a duplex, rise and twist (Fig. 1), namely the distances and the dihedral angles between base pairs, respectively. The hole mobility in an ideally ordered poly(G)-poly(C) duplex was found to be decreased by two orders of magnitude due to twisting of base pairs and static energy disorder. A hole mobility of 0.1 cm V s was predicted for a homogeneous system the mobility of natural duplexes is expected to be much lower [33]. In this context, one can mention several theoretical studies, based on band structure approaches, to estimate the electrical conductivity of DNA [85-87]. 

Properties of the membrane studied included the pressure on all six faces of the simulated volume, displacements of lipid molecules and atomic displacements, deuterium order parameter (S p) as a function of chain position, fluctuations of chain and head group dihedral angles, penetration of water, surface area per lipid molecule, and the lipid self-diffusion coefficient. Interesting re-... 

It is of interest to examine the nature of the motions of a sidechain as large as a tryptophan residue in the protein interior. Reorientation of the transition dipole vector of tryptophan is due mainly to rotation about the C —C(3 and C,3—Cr bonds, which correspond to the x1 and x2 dihedral angles of the side-chain, although larger-scale collective motions of the backbone are also involved. In the protein environment, the fluctuations of x1 and x2 are expected to be anticorrelated so that large variations in the two angles result in a... 

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